diff --git a/bin/yunohost-api b/bin/yunohost-api
index 6e47df7ef..e518c34b0 100755
--- a/bin/yunohost-api
+++ b/bin/yunohost-api
@@ -201,12 +201,10 @@ if __name__ == '__main__':
     _init_moulinette(opts.use_websocket, opts.debug, opts.verbose)
 
     # Run the server
-    from yunohost.utils.packages import ynh_packages_version
     ret = moulinette.api(
         _retrieve_namespaces(),
         host=opts.host, port=opts.port, routes={
             ('GET', '/installed'): is_installed,
-            ('GET', '/version'): ynh_packages_version,
         }, use_cache=opts.use_cache, use_websocket=opts.use_websocket
     )
     sys.exit(ret)
diff --git a/data/helpers.d/backend b/data/helpers.d/backend
index c96315238..1532601a8 100644
--- a/data/helpers.d/backend
+++ b/data/helpers.d/backend
@@ -288,3 +288,150 @@ ynh_remove_fpm_config () {
 	ynh_secure_remove --file="$fpm_config_dir/conf.d/20-$app.ini" 2>&1
 	sudo systemctl reload $fpm_service
 }
+
+# Create a dedicated fail2ban config (jail and filter conf files)
+#
+# usage 1: ynh_add_fail2ban_config --logpath=log_file --failregex=filter [--max_retry=max_retry] [--ports=ports]
+# | arg: -l, --logpath=   - Log file to be checked by fail2ban
+# | arg: -r, --failregex= - Failregex to be looked for by fail2ban
+# | arg: -m, --max_retry= - Maximum number of retries allowed before banning IP address - default: 3
+# | arg: -p, --ports=     - Ports blocked for a banned IP address - default: http,https
+#
+# -----------------------------------------------------------------------------
+#
+# usage 2: ynh_add_fail2ban_config --use_template [--others_var="list of others variables to replace"]
+# | arg: -t, --use_template - Use this helper in template mode
+# | arg: -v, --others_var=  - List of others variables to replace separeted by a space
+# |                           for example : 'var_1 var_2 ...'
+#
+# This will use a template in ../conf/f2b_jail.conf and ../conf/f2b_filter.conf
+#   __APP__      by  $app
+#
+#  You can dynamically replace others variables by example :
+#   __VAR_1__    by $var_1
+#   __VAR_2__    by $var_2
+#
+# Generally your template will look like that by example (for synapse):
+#
+# f2b_jail.conf:
+#     [__APP__]
+#     enabled = true
+#     port = http,https
+#     filter = __APP__
+#     logpath = /var/log/__APP__/logfile.log
+#     maxretry = 3
+#
+# f2b_filter.conf:
+#     [INCLUDES]
+#     before = common.conf
+#     [Definition]
+#
+#     # Part of regex definition (just used to make more easy to make the global regex)
+#     __synapse_start_line = .? \- synapse\..+ \-
+#
+#    # Regex definition.
+#    failregex = ^%(__synapse_start_line)s INFO \- POST\-(\d+)\- <HOST> \- \d+ \- Received request\: POST /_matrix/client/r0/login\??<SKIPLINES>%(__synapse_start_line)s INFO \- POST\-\1\- Got login request with identifier: \{u'type': u'm.id.user', u'user'\: u'(.+?)'\}, medium\: None, address: None, user\: u'\5'<SKIPLINES>%(__synapse_start_line)s WARNING \- \- (Attempted to login as @\5\:.+ but they do not exist|Failed password login for user @\5\:.+)$
+#
+#     ignoreregex =
+#
+# -----------------------------------------------------------------------------
+#
+# Note about the "failregex" option:
+#          regex to match the password failure messages in the logfile. The
+#          host must be matched by a group named "host". The tag "<HOST>" can
+#          be used for standard IP/hostname matching and is only an alias for
+#          (?:::f{4,6}:)?(?P<host>[\w\-.^_]+)
+#
+#          You can find some more explainations about how to make a regex here :
+#          https://www.fail2ban.org/wiki/index.php/MANUAL_0_8#Filters
+#
+# Note that the logfile need to exist before to call this helper !!
+#
+# To validate your regex you can test with this command:
+# fail2ban-regex /var/log/YOUR_LOG_FILE_PATH /etc/fail2ban/filter.d/YOUR_APP.conf
+#
+ynh_add_fail2ban_config () {
+  # Declare an array to define the options of this helper.
+  local legacy_args=lrmptv
+  declare -Ar args_array=( [l]=logpath= [r]=failregex= [m]=max_retry= [p]=ports= [t]=use_template [v]=others_var=)
+  local logpath
+  local failregex
+  local max_retry
+  local ports
+  local others_var
+  local use_template
+  # Manage arguments with getopts
+  ynh_handle_getopts_args "$@"
+  use_template="${use_template:-0}"
+  max_retry=${max_retry:-3}
+  ports=${ports:-http,https}
+
+  finalfail2banjailconf="/etc/fail2ban/jail.d/$app.conf"
+  finalfail2banfilterconf="/etc/fail2ban/filter.d/$app.conf"
+  ynh_backup_if_checksum_is_different "$finalfail2banjailconf"
+  ynh_backup_if_checksum_is_different "$finalfail2banfilterconf"
+
+  if [ $use_template -eq 1 ]
+  then
+    # Usage 2, templates
+    cp ../conf/f2b_jail.conf $finalfail2banjailconf
+    cp ../conf/f2b_filter.conf $finalfail2banfilterconf
+
+    if [ -n "${app:-}" ]
+    then
+      ynh_replace_string "__APP__" "$app" "$finalfail2banjailconf"
+      ynh_replace_string "__APP__" "$app" "$finalfail2banfilterconf"
+    fi
+
+    # Replace all other variable given as arguments
+    for var_to_replace in ${others_var:-}; do
+      # ${var_to_replace^^} make the content of the variable on upper-cases
+      # ${!var_to_replace} get the content of the variable named $var_to_replace
+      ynh_replace_string --match_string="__${var_to_replace^^}__" --replace_string="${!var_to_replace}" --target_file="$finalfail2banjailconf"
+      ynh_replace_string --match_string="__${var_to_replace^^}__" --replace_string="${!var_to_replace}" --target_file="$finalfail2banfilterconf"
+    done
+
+  else
+    # Usage 1, no template. Build a config file from scratch.
+    test -n "$logpath" || ynh_die "ynh_add_fail2ban_config expects a logfile path as first argument and received nothing."
+    test -n "$failregex" || ynh_die "ynh_add_fail2ban_config expects a failure regex as second argument and received nothing."
+
+    tee $finalfail2banjailconf <<EOF
+[$app]
+enabled = true
+port = $ports
+filter = $app
+logpath = $logpath
+maxretry = $max_retry
+EOF
+
+    tee $finalfail2banfilterconf <<EOF
+[INCLUDES]
+before = common.conf
+[Definition]
+failregex = $failregex
+ignoreregex =
+EOF
+  fi
+
+  # Common to usage 1 and 2.
+  ynh_store_file_checksum "$finalfail2banjailconf"
+  ynh_store_file_checksum "$finalfail2banfilterconf"
+
+  systemctl try-reload-or-restart fail2ban
+
+  local fail2ban_error="$(journalctl -u fail2ban | tail -n50 | grep "WARNING.*$app.*")"
+  if [[ -n "$fail2ban_error" ]]; then
+    ynh_print_err --message="Fail2ban failed to load the jail for $app"
+    ynh_print_warn --message="${fail2ban_error#*WARNING}"
+  fi
+}
+
+# Remove the dedicated fail2ban config (jail and filter conf files)
+#
+# usage: ynh_remove_fail2ban_config
+ynh_remove_fail2ban_config () {
+  ynh_secure_remove "/etc/fail2ban/jail.d/$app.conf"
+  ynh_secure_remove "/etc/fail2ban/filter.d/$app.conf"
+  systemctl try-reload-or-restart fail2ban
+}
diff --git a/data/helpers.d/debug b/data/helpers.d/debug
new file mode 100644
index 000000000..a8b7c8d69
--- /dev/null
+++ b/data/helpers.d/debug
@@ -0,0 +1,59 @@
+#!/bin/bash
+
+# Debugger for app packagers
+#
+# usage: ynh_debug [--message=message] [--trace=1/0]
+# | arg: -m, --message= - The text to print
+# | arg: -t, --trace=   - Turn on or off the trace of the script. Usefull to trace nonly a small part of a script.
+ynh_debug () {
+	# Disable set xtrace for the helper itself, to not pollute the debug log
+	set +x
+	# Declare an array to define the options of this helper.
+	local legacy_args=mt
+	declare -Ar args_array=( [m]=message= [t]=trace= )
+	local message
+	local trace
+	# Manage arguments with getopts
+	ynh_handle_getopts_args "$@"
+	# Redisable xtrace, ynh_handle_getopts_args set it back
+	set +x
+	message=${message:-}
+	trace=${trace:-}
+
+	if [ -n "$message" ]
+	then
+		ynh_print_log "\e[34m\e[1m[DEBUG]\e[0m ${message}" >&2
+	fi
+
+	if [ "$trace" == "1" ]
+	then
+		ynh_debug --message="Enable debugging"
+		set +x
+		# Get the current file descriptor of xtrace
+		old_bash_xtracefd=$BASH_XTRACEFD
+		# Add the current file name and the line number of any command currently running while tracing.
+		PS4='$(basename ${BASH_SOURCE[0]})-L${LINENO}: '
+		# Force xtrace to stderr
+		BASH_XTRACEFD=2
+	fi
+	if [ "$trace" == "0" ]
+	then
+		ynh_debug --message="Disable debugging"
+		set +x
+		# Put xtrace back to its original fild descriptor
+		BASH_XTRACEFD=$old_bash_xtracefd
+	fi
+	# Renable set xtrace
+	set -x
+}
+
+# Execute a command and print the result as debug
+#
+# usage: ynh_debug_exec command to execute
+# usage: ynh_debug_exec "command to execute | following command"
+# In case of use of pipes, you have to use double quotes. Otherwise, this helper will be executed with the first command, then be sent to the next pipe.
+#
+# | arg: command - command to execute
+ynh_debug_exec () {
+	ynh_debug --message="$(eval $@)"
+}
diff --git a/data/helpers.d/filesystem b/data/helpers.d/filesystem
index 88d51750b..10123dea4 100644
--- a/data/helpers.d/filesystem
+++ b/data/helpers.d/filesystem
@@ -323,6 +323,16 @@ ynh_store_file_checksum () {
 
 	local checksum_setting_name=checksum_${file//[\/ ]/_}	# Replace all '/' and ' ' by '_'
 	ynh_app_setting_set --app=$app --key=$checksum_setting_name --value=$(sudo md5sum "$file" | cut -d' ' -f1)
+
+	# If backup_file_checksum isn't empty, ynh_backup_if_checksum_is_different has made a backup
+	if [ -n "${backup_file_checksum-}" ]
+	then
+		# Print the diff between the previous file and the new one.
+		# diff return 1 if the files are different, so the || true
+		diff --report-identical-files --unified --color=always $backup_file_checksum $file >&2 || true
+	fi
+	# Unset the variable, so it wouldn't trig a ynh_store_file_checksum without a ynh_backup_if_checksum_is_different before it.
+	unset backup_file_checksum
 }
 
 # Verify the checksum and backup the file if it's different
@@ -345,15 +355,17 @@ ynh_backup_if_checksum_is_different () {
 
 	local checksum_setting_name=checksum_${file//[\/ ]/_}	# Replace all '/' and ' ' by '_'
 	local checksum_value=$(ynh_app_setting_get --app=$app --key=$checksum_setting_name)
+	# backup_file_checksum isn't declare as local, so it can be reuse by ynh_store_file_checksum
+	backup_file_checksum=""
 	if [ -n "$checksum_value" ]
 	then	# Proceed only if a value was stored into the app settings
 		if ! echo "$checksum_value $file" | sudo md5sum -c --status
 		then	# If the checksum is now different
-			local backup_file="/home/yunohost.conf/backup/$file.backup.$(date '+%Y%m%d.%H%M%S')"
-			sudo mkdir -p "$(dirname "$backup_file")"
-			sudo cp -a "$file" "$backup_file"	# Backup the current file
-			echo "File $file has been manually modified since the installation or last upgrade. So it has been duplicated in $backup_file" >&2
-			echo "$backup_file"	# Return the name of the backup file
+			backup_file_checksum="/home/yunohost.conf/backup/$file.backup.$(date '+%Y%m%d.%H%M%S')"
+			sudo mkdir -p "$(dirname "$backup_file_checksum")"
+			sudo cp -a "$file" "$backup_file_checksum"	# Backup the current file
+			ynh_print_warn "File $file has been manually modified since the installation or last upgrade. So it has been duplicated in $backup_file_checksum"
+			echo "$backup_file_checksum"	# Return the name of the backup file
 		fi
 	fi
 }
diff --git a/data/helpers.d/nodejs b/data/helpers.d/nodejs
index c4332b60c..098ed4410 100644
--- a/data/helpers.d/nodejs
+++ b/data/helpers.d/nodejs
@@ -98,7 +98,13 @@ ynh_install_nodejs () {
 	test -x /usr/bin/npm_n && mv /usr/bin/npm_n /usr/bin/npm
 
 	# Install the requested version of nodejs
-	n $nodejs_version
+	uname=$(uname -m)
+	if [[ $uname =~ aarch64 || $uname =~ arm64 ]]
+	then
+		n $nodejs_version --arch=arm64
+	else
+		n $nodejs_version
+	fi
 
 	# Find the last "real" version for this major version of node.
 	real_nodejs_version=$(find $node_version_path/$nodejs_version* -maxdepth 0 | sort --version-sort | tail --lines=1)
diff --git a/data/helpers.d/package b/data/helpers.d/package
index c0617abb2..000b0ee74 100644
--- a/data/helpers.d/package
+++ b/data/helpers.d/package
@@ -17,6 +17,21 @@ ynh_wait_dpkg_free() {
             # Sleep an exponential time at each round
             sleep $(( try * try ))
         else
+            # Check if dpkg hasn't been interrupted and is fully available.
+            # See this for more information: https://sources.debian.org/src/apt/1.4.9/apt-pkg/deb/debsystem.cc/#L141-L174
+            local dpkg_dir="/var/lib/dpkg/updates/"
+
+            # For each file in $dpkg_dir
+            while read dpkg_file <&9
+            do
+                # Check if the name of this file contains only numbers.
+                if echo "$dpkg_file" | grep -Pq "^[[:digit:]]+$"
+                then
+                    # If so, that a remaining of dpkg.
+                    ynh_print_err "E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem."
+                    return 1
+                fi
+            done 9<<< "$(ls -1 $dpkg_dir)"
             return 0
         fi
     done
@@ -71,7 +86,7 @@ ynh_package_version() {
 # usage: ynh_apt update
 ynh_apt() {
     ynh_wait_dpkg_free
-    DEBIAN_FRONTEND=noninteractive sudo apt-get -y $@
+    DEBIAN_FRONTEND=noninteractive apt-get -y $@
 }
 
 # Update package index files
diff --git a/data/helpers.d/print b/data/helpers.d/print
index 7f37021ae..b46192d87 100644
--- a/data/helpers.d/print
+++ b/data/helpers.d/print
@@ -89,6 +89,7 @@ ynh_print_err () {
 # usage: ynh_exec_err command to execute
 # usage: ynh_exec_err "command to execute | following command"
 # In case of use of pipes, you have to use double quotes. Otherwise, this helper will be executed with the first command, then be sent to the next pipe.
+# If the command to execute uses double quotes, they have to be escaped or they will be interpreted and removed.
 #
 # | arg: command - command to execute
 ynh_exec_err () {
@@ -100,6 +101,7 @@ ynh_exec_err () {
 # usage: ynh_exec_warn command to execute
 # usage: ynh_exec_warn "command to execute | following command"
 # In case of use of pipes, you have to use double quotes. Otherwise, this helper will be executed with the first command, then be sent to the next pipe.
+# If the command to execute uses double quotes, they have to be escaped or they will be interpreted and removed.
 #
 # | arg: command - command to execute
 ynh_exec_warn () {
@@ -111,6 +113,7 @@ ynh_exec_warn () {
 # usage: ynh_exec_warn_less command to execute
 # usage: ynh_exec_warn_less "command to execute | following command"
 # In case of use of pipes, you have to use double quotes. Otherwise, this helper will be executed with the first command, then be sent to the next pipe.
+# If the command to execute uses double quotes, they have to be escaped or they will be interpreted and removed.
 #
 # | arg: command - command to execute
 ynh_exec_warn_less () {
@@ -122,6 +125,7 @@ ynh_exec_warn_less () {
 # usage: ynh_exec_quiet command to execute
 # usage: ynh_exec_quiet "command to execute | following command"
 # In case of use of pipes, you have to use double quotes. Otherwise, this helper will be executed with the first command, then be sent to the next pipe.
+# If the command to execute uses double quotes, they have to be escaped or they will be interpreted and removed.
 #
 # | arg: command - command to execute
 ynh_exec_quiet () {
@@ -133,6 +137,7 @@ ynh_exec_quiet () {
 # usage: ynh_exec_fully_quiet command to execute
 # usage: ynh_exec_fully_quiet "command to execute | following command"
 # In case of use of pipes, you have to use double quotes. Otherwise, this helper will be executed with the first command, then be sent to the next pipe.
+# If the command to execute uses double quotes, they have to be escaped or they will be interpreted and removed.
 #
 # | arg: command - command to execute
 ynh_exec_fully_quiet () {
diff --git a/data/helpers.d/system b/data/helpers.d/system
index 968135f16..9a4219e11 100644
--- a/data/helpers.d/system
+++ b/data/helpers.d/system
@@ -55,3 +55,107 @@ ynh_abort_if_errors () {
 ynh_get_debian_release () {
 	echo $(lsb_release --codename --short)
 }
+
+# Read the value of a key in a ynh manifest file
+#
+# usage: ynh_read_manifest manifest key
+# | arg: -m, --manifest= - Path of the manifest to read
+# | arg: -k, --key= - Name of the key to find
+ynh_read_manifest () {
+	# Declare an array to define the options of this helper.
+        declare -Ar args_array=( [m]=manifest= [k]=manifest_key= )
+        local manifest
+        local manifest_key
+	# Manage arguments with getopts
+	ynh_handle_getopts_args "$@"
+
+	if [ ! -e "$manifest" ]; then
+		# If the manifest isn't found, try the common place for backup and restore script.
+		manifest="../settings/manifest.json"
+	fi
+
+	jq ".$manifest_key" "$manifest" --raw-output
+}
+
+# Read the upstream version from the manifest
+# The version number in the manifest is defined by <upstreamversion>~ynh<packageversion>
+# For example : 4.3-2~ynh3
+# This include the number before ~ynh
+# In the last example it return 4.3-2
+#
+# usage: ynh_app_upstream_version [-m manifest]
+# | arg: -m, --manifest= - Path of the manifest to read
+ynh_app_upstream_version () {
+    declare -Ar args_array=( [m]=manifest= )
+    local manifest
+    # Manage arguments with getopts
+    ynh_handle_getopts_args "$@"
+
+    manifest="${manifest:-../manifest.json}"
+    version_key=$(ynh_read_manifest --manifest="$manifest" --manifest_key="version")
+    echo "${version_key/~ynh*/}"
+}
+
+# Read package version from the manifest
+# The version number in the manifest is defined by <upstreamversion>~ynh<packageversion>
+# For example : 4.3-2~ynh3
+# This include the number after ~ynh
+# In the last example it return 3
+#
+# usage: ynh_app_package_version [-m manifest]
+# | arg: -m, --manifest= - Path of the manifest to read
+ynh_app_package_version () {
+    declare -Ar args_array=( [m]=manifest= )
+    local manifest
+    # Manage arguments with getopts
+    ynh_handle_getopts_args "$@"
+
+    manifest="${manifest:-../manifest.json}"
+    version_key=$(ynh_read_manifest --manifest="$manifest" --manifest_key="version")
+    echo "${version_key/*~ynh/}"
+}
+
+# Checks the app version to upgrade with the existing app version and returns:
+# - UPGRADE_APP if the upstream app version has changed
+# - UPGRADE_PACKAGE if only the YunoHost package has changed
+#
+## It stops the current script without error if the package is up-to-date
+#
+# This helper should be used to avoid an upgrade of an app, or the upstream part
+# of it, when it's not needed
+#
+# To force an upgrade, even if the package is up to date,
+# you have to set the variable YNH_FORCE_UPGRADE before.
+# example: sudo YNH_FORCE_UPGRADE=1 yunohost app upgrade MyApp
+#
+# usage: ynh_check_app_version_changed
+ynh_check_app_version_changed () {
+  local force_upgrade=${YNH_FORCE_UPGRADE:-0}
+  local package_check=${PACKAGE_CHECK_EXEC:-0}
+
+  # By default, upstream app version has changed
+  local return_value="UPGRADE_APP"
+
+  local current_version=$(ynh_read_manifest --manifest="/etc/yunohost/apps/$YNH_APP_INSTANCE_NAME/manifest.json" --manifest_key="version" || echo 1.0)
+  local current_upstream_version="$(ynh_app_upstream_version --manifest="/etc/yunohost/apps/$YNH_APP_INSTANCE_NAME/manifest.json")"
+  local update_version=$(ynh_read_manifest --manifest="../manifest.json" --manifest_key="version" || echo 1.0)
+  local update_upstream_version="$(ynh_app_upstream_version)"
+
+  if [ "$current_version" == "$update_version" ] ; then
+      # Complete versions are the same
+      if [ "$force_upgrade" != "0" ]
+      then
+        echo "Upgrade forced by YNH_FORCE_UPGRADE." >&2
+        unset YNH_FORCE_UPGRADE
+      elif [ "$package_check" != "0" ]
+      then
+        echo "Upgrade forced for package check." >&2
+      else
+        ynh_die "Up-to-date, nothing to do" 0
+      fi
+  elif [ "$current_upstream_version" == "$update_upstream_version" ] ; then
+    # Upstream versions are the same, only YunoHost package versions differ
+    return_value="UPGRADE_PACKAGE"
+  fi
+  echo $return_value
+}
diff --git a/data/helpers.d/utils b/data/helpers.d/utils
index 360174847..5ba2946a2 100644
--- a/data/helpers.d/utils
+++ b/data/helpers.d/utils
@@ -257,7 +257,14 @@ ynh_setup_source () {
 # | arg: ...         - (Optionnal) More POST keys and values
 ynh_local_curl () {
 	# Define url of page to curl
-	local full_page_url=https://localhost$path_url$1
+	local local_page=$(ynh_normalize_url_path $1)
+	local full_path=$path_url$local_page
+	
+	if [ "${path_url}" == "/" ]; then 
+		full_path=$local_page
+	fi
+	
+	local full_page_url=https://localhost$full_path
 
 	# Concatenate all other arguments with '&' to prepare POST data
 	local POST_data=""
diff --git a/data/hooks/backup/05-conf_ldap b/data/hooks/backup/05-conf_ldap
index b21103ede..9ae22095e 100755
--- a/data/hooks/backup/05-conf_ldap
+++ b/data/hooks/backup/05-conf_ldap
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/ldap"
diff --git a/data/hooks/backup/08-conf_ssh b/data/hooks/backup/08-conf_ssh
index ae422617e..ee976080c 100755
--- a/data/hooks/backup/08-conf_ssh
+++ b/data/hooks/backup/08-conf_ssh
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/ssh"
diff --git a/data/hooks/backup/11-conf_ynh_mysql b/data/hooks/backup/11-conf_ynh_mysql
index 60bd8c017..031707337 100755
--- a/data/hooks/backup/11-conf_ynh_mysql
+++ b/data/hooks/backup/11-conf_ynh_mysql
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/ynh/mysql"
diff --git a/data/hooks/backup/14-conf_ssowat b/data/hooks/backup/14-conf_ssowat
index ca42d3369..d4db72493 100755
--- a/data/hooks/backup/14-conf_ssowat
+++ b/data/hooks/backup/14-conf_ssowat
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/ssowat"
diff --git a/data/hooks/backup/17-data_home b/data/hooks/backup/17-data_home
index f7a797b6b..af00d67e8 100755
--- a/data/hooks/backup/17-data_home
+++ b/data/hooks/backup/17-data_home
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/data/home"
diff --git a/data/hooks/backup/20-conf_ynh_firewall b/data/hooks/backup/20-conf_ynh_firewall
index 4e08114e7..98be3eb09 100755
--- a/data/hooks/backup/20-conf_ynh_firewall
+++ b/data/hooks/backup/20-conf_ynh_firewall
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/ynh/firewall"
diff --git a/data/hooks/backup/21-conf_ynh_certs b/data/hooks/backup/21-conf_ynh_certs
index f9687164d..a3912a995 100755
--- a/data/hooks/backup/21-conf_ynh_certs
+++ b/data/hooks/backup/21-conf_ynh_certs
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/ynh/certs"
diff --git a/data/hooks/backup/23-data_mail b/data/hooks/backup/23-data_mail
index 618a0aafe..7fdc883fd 100755
--- a/data/hooks/backup/23-data_mail
+++ b/data/hooks/backup/23-data_mail
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/data/mail"
diff --git a/data/hooks/backup/26-conf_xmpp b/data/hooks/backup/26-conf_xmpp
index 12300a00a..b55ad2bfc 100755
--- a/data/hooks/backup/26-conf_xmpp
+++ b/data/hooks/backup/26-conf_xmpp
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/xmpp"
diff --git a/data/hooks/backup/29-conf_nginx b/data/hooks/backup/29-conf_nginx
index d900c7535..81e145e24 100755
--- a/data/hooks/backup/29-conf_nginx
+++ b/data/hooks/backup/29-conf_nginx
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/nginx"
diff --git a/data/hooks/backup/32-conf_cron b/data/hooks/backup/32-conf_cron
index 2fea9f53f..063ec1a3f 100755
--- a/data/hooks/backup/32-conf_cron
+++ b/data/hooks/backup/32-conf_cron
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/cron"
diff --git a/data/hooks/backup/40-conf_ynh_currenthost b/data/hooks/backup/40-conf_ynh_currenthost
index e4a684576..6a98fd0d2 100755
--- a/data/hooks/backup/40-conf_ynh_currenthost
+++ b/data/hooks/backup/40-conf_ynh_currenthost
@@ -4,7 +4,7 @@
 set -eu
 
 # Source YNH helpers
-source /usr/share/yunohost/helpers.d/filesystem
+source /usr/share/yunohost/helpers
 
 # Backup destination
 backup_dir="${1}/conf/ynh"
diff --git a/data/hooks/conf_regen/03-ssh b/data/hooks/conf_regen/03-ssh
index 9de527518..5bb9cf916 100755
--- a/data/hooks/conf_regen/03-ssh
+++ b/data/hooks/conf_regen/03-ssh
@@ -2,7 +2,7 @@
 
 set -e
 
-. /usr/share/yunohost/helpers.d/utils
+. /usr/share/yunohost/helpers
 
 do_pre_regen() {
     pending_dir=$1
diff --git a/data/hooks/conf_regen/15-nginx b/data/hooks/conf_regen/15-nginx
index 461c10c0c..7ca63c003 100755
--- a/data/hooks/conf_regen/15-nginx
+++ b/data/hooks/conf_regen/15-nginx
@@ -2,7 +2,7 @@
 
 set -e
 
-. /usr/share/yunohost/helpers.d/utils
+. /usr/share/yunohost/helpers
 
 do_init_regen() {
   if [[ $EUID -ne 0 ]]; then
diff --git a/data/hooks/conf_regen/34-mysql b/data/hooks/conf_regen/34-mysql
index 5ee91827b..9f35fec18 100755
--- a/data/hooks/conf_regen/34-mysql
+++ b/data/hooks/conf_regen/34-mysql
@@ -2,6 +2,7 @@
 
 set -e
 MYSQL_PKG="mariadb-server-10.1"
+. /usr/share/yunohost/helpers
 
 do_pre_regen() {
   pending_dir=$1
@@ -15,7 +16,6 @@ do_post_regen() {
   regen_conf_files=$1
 
   if [ ! -f /etc/yunohost/mysql ]; then
-      . /usr/share/yunohost/helpers.d/string
 
       # ensure that mysql is running
       sudo systemctl -q is-active mysql.service \
@@ -25,8 +25,6 @@ do_post_regen() {
       mysql_password=$(ynh_string_random 10)
       sudo mysqladmin -s -u root -pyunohost password "$mysql_password" || {
         if [ $FORCE -eq 1 ]; then
-            . /usr/share/yunohost/helpers.d/package
-
             echo "It seems that you have already configured MySQL." \
               "YunoHost needs to have a root access to MySQL to runs its" \
               "applications, and is going to reset the MySQL root password." \
diff --git a/data/hooks/conf_regen/43-dnsmasq b/data/hooks/conf_regen/43-dnsmasq
index 2c8ce797b..ed795c058 100755
--- a/data/hooks/conf_regen/43-dnsmasq
+++ b/data/hooks/conf_regen/43-dnsmasq
@@ -1,13 +1,11 @@
 #!/bin/bash
 
 set -e
+. /usr/share/yunohost/helpers
 
 do_pre_regen() {
   pending_dir=$1
 
-  # source ip helpers
-  . /usr/share/yunohost/helpers.d/ip
-
   cd /usr/share/yunohost/templates/dnsmasq
 
   # create directory for pending conf
diff --git a/data/hooks/restore/11-conf_ynh_mysql b/data/hooks/restore/11-conf_ynh_mysql
index 0aaaccd54..1336a2cc2 100644
--- a/data/hooks/restore/11-conf_ynh_mysql
+++ b/data/hooks/restore/11-conf_ynh_mysql
@@ -1,6 +1,8 @@
 backup_dir="$1/conf/ynh/mysql"
 MYSQL_PKG="mariadb-server-10.1"
 
+. /usr/share/yunohost/helpers
+
 # ensure that mysql is running
 service mysql status >/dev/null 2>&1 \
   || service mysql start
@@ -11,13 +13,11 @@ service mysql status >/dev/null 2>&1 \
 new_pwd=$(sudo cat "${backup_dir}/root_pwd" || sudo cat "${backup_dir}/mysql")
 [ -z "$curr_pwd" ] && curr_pwd="yunohost"
 [ -z "$new_pwd" ] && {
-    . /usr/share/yunohost/helpers.d/string
     new_pwd=$(ynh_string_random 10)
 }
 
 # attempt to change it
 sudo mysqladmin -s -u root -p"$curr_pwd" password "$new_pwd" || {
-  . /usr/share/yunohost/helpers.d/package
 
   echo "It seems that you have already configured MySQL." \
     "YunoHost needs to have a root access to MySQL to runs its" \
diff --git a/data/templates/dnsmasq/plain/resolv.dnsmasq.conf b/data/templates/dnsmasq/plain/resolv.dnsmasq.conf
index 7eed1142f..197ee2d64 100644
--- a/data/templates/dnsmasq/plain/resolv.dnsmasq.conf
+++ b/data/templates/dnsmasq/plain/resolv.dnsmasq.conf
@@ -9,25 +9,37 @@
 
 # (FR) FDN
 nameserver 80.67.169.12
+nameserver 2001:910:800::12
 nameserver 80.67.169.40
+nameserver 2001:910:800::40
 # (FR) LDN
 nameserver 80.67.188.188
+nameserver 2001:913::8
 # (FR) ARN
 nameserver 89.234.141.66
+nameserver 2a00:5881:8100:1000::3
 # (FR) Aquilenet
 nameserver 185.233.100.100
+nameserver 2a0c:e300::100
 nameserver 185.233.100.101
+nameserver 2a0c:e300::101
 # (FR) gozmail / grifon
 nameserver 80.67.190.200
+nameserver 2a00:5884:8218::1
 # (DE) FoeBud / Digital Courage
 nameserver 85.214.20.141
 # (DE) CCC Berlin
 nameserver 195.160.173.53
 # (DE) AS250
 nameserver 194.150.168.168
+nameserver 2001:4ce8::53
 # (DE) Ideal-Hosting
 nameserver 84.200.69.80
+nameserver 2001:1608:10:25::1c04:b12f
 nameserver 84.200.70.40
+nameserver 2001:1608:10:25::9249:d69b
 # (DK) censurfridns
 nameserver 91.239.100.100
+nameserver 2001:67c:28a4::
 nameserver 89.233.43.71
+nameserver 2002:d596:2a92:1:71:53::
diff --git a/data/templates/nginx/plain/yunohost_admin.conf b/data/templates/nginx/plain/yunohost_admin.conf
index b6fabf8e3..2493e4033 100644
--- a/data/templates/nginx/plain/yunohost_admin.conf
+++ b/data/templates/nginx/plain/yunohost_admin.conf
@@ -60,7 +60,8 @@ server {
         if ($http_user_agent ~ (crawl|Googlebot|Slurp|spider|bingbot|tracker|click|parser|spider|facebookexternalhit) ) {
             return 403;
         }
-
+        # X-Robots-Tag to precise the rules applied.
+        add_header  X-Robots-Tag "nofollow, noindex, noarchive, nosnippet";
         # Redirect most of 404 to maindomain.tld/yunohost/sso
         access_by_lua_file /usr/share/ssowat/access.lua;
     }
diff --git a/data/templates/nginx/server.tpl.conf b/data/templates/nginx/server.tpl.conf
index 0c221f188..43d38ca98 100644
--- a/data/templates/nginx/server.tpl.conf
+++ b/data/templates/nginx/server.tpl.conf
@@ -51,7 +51,9 @@ server {
     # Follows the Web Security Directives from the Mozilla Dev Lab and the Mozilla Obervatory + Partners
     # https://wiki.mozilla.org/Security/Guidelines/Web_Security
     # https://observatory.mozilla.org/ 
-    more_set_headers "Strict-Transport-Security : max-age=63072000; includeSubDomains; preload"; 
+    {% if domain_cert_ca != "Self-signed" %}
+    more_set_headers "Strict-Transport-Security : max-age=63072000; includeSubDomains; preload";
+    {% endif %}
     more_set_headers "Content-Security-Policy : upgrade-insecure-requests";
     more_set_headers "Content-Security-Policy-Report-Only : default-src https: data: 'unsafe-inline' 'unsafe-eval'";
     more_set_headers "X-Content-Type-Options : nosniff";
diff --git a/debian/changelog b/debian/changelog
index 3f3a6a5ef..7be4212fe 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+yunohost (3.4.2.4) stable; urgency=low
+
+  - [fix] Meltdown vulnerability checker something outputing trash instead of pure json
+
+ -- Alexandre Aubin <alex.aubin@mailoo.org>  Tue, 19 Feb 2019 19:11:38  +0000
+
 yunohost (3.4.2.3) stable; urgency=low
 
   - [fix] Admin password appearing in logs after logging in on webadmin
diff --git a/debian/control b/debian/control
index b359d5ec4..685c194ba 100644
--- a/debian/control
+++ b/debian/control
@@ -13,7 +13,7 @@ Depends: ${python:Depends}, ${misc:Depends}
  , moulinette (>= 2.7.1), ssowat (>= 2.7.1)
  , python-psutil, python-requests, python-dnspython, python-openssl
  , python-apt, python-miniupnpc, python-dbus, python-jinja2
- , glances
+ , glances, apt-transport-https
  , dnsutils, bind9utils, unzip, git, curl, cron, wget, jq
  , ca-certificates, netcat-openbsd, iproute
  , mariadb-server, php-mysql | php-mysqlnd
diff --git a/locales/en.json b/locales/en.json
index ca1d9c8a1..47e452450 100644
--- a/locales/en.json
+++ b/locales/en.json
@@ -24,7 +24,8 @@
     "app_location_install_failed": "Unable to install the app in this location because it conflit with the app '{other_app}' already installed on '{other_path}'",
     "app_location_unavailable": "This url is not available or conflicts with the already installed app(s):\n{apps:s}",
     "app_manifest_invalid": "Invalid app manifest: {error}",
-    "app_no_upgrade": "No app to upgrade",
+    "app_no_upgrade": "No apps to upgrade",
+    "app_not_upgraded": "The following apps were not upgraded: {apps}",
     "app_not_correctly_installed": "{app:s} seems to be incorrectly installed",
     "app_not_installed": "{app:s} is not installed",
     "app_not_properly_removed": "{app:s} has not been properly removed",
@@ -34,9 +35,14 @@
     "app_requirements_failed": "Unable to meet requirements for {app}: {error}",
     "app_requirements_unmeet": "Requirements are not met for {app}, the package {pkgname} ({version}) must be {spec}",
     "app_sources_fetch_failed": "Unable to fetch sources files",
+    "app_start_install": "Installing application {app}…",
+    "app_start_remove": "Removing application {app}…",
+    "app_start_backup": "Collecting files to be backuped for {app}…",
+    "app_start_restore": "Restoring application {app}…",
     "app_unknown": "Unknown app",
     "app_unsupported_remote_type": "Unsupported remote type used for the app",
-    "app_upgrade_app_name": "Upgrading app {app}…",
+    "app_upgrade_several_apps": "The following apps will be upgraded : {apps}",
+    "app_upgrade_app_name": "Now upgrading app {app}…",
     "app_upgrade_failed": "Unable to upgrade {app:s}",
     "app_upgrade_some_app_failed": "Unable to upgrade some applications",
     "app_upgraded": "{app:s} has been upgraded",
@@ -63,6 +69,7 @@
     "ask_path": "Path",
     "backup_abstract_method": "This backup method hasn't yet been implemented",
     "backup_action_required": "You must specify something to save",
+    "backup_actually_backuping": "Now creating a backup archive from the files collected…",
     "backup_app_failed": "Unable to back up the app '{app:s}'",
     "backup_applying_method_borg": "Sending all files to backup into borg-backup repository…",
     "backup_applying_method_copy": "Copying all files to backup…",
@@ -75,7 +82,7 @@
     "backup_archive_name_unknown": "Unknown local backup archive named '{name:s}'",
     "backup_archive_open_failed": "Unable to open the backup archive",
     "backup_archive_system_part_not_available": "System part '{part:s}' not available in this backup",
-    "backup_archive_writing_error": "Unable to add files to backup into the compressed archive",
+    "backup_archive_writing_error": "Unable to add files '{source:s}' (named in the archive: '{dest:s}') to backup into the compressed archive '{archive:s}'",
     "backup_ask_for_copying_if_needed": "Some files couldn't be prepared to be backuped using the method that avoid to temporarily waste space on the system. To perform the backup, {size:s}MB should be used temporarily. Do you agree?",
     "backup_borg_not_implemented": "Borg backup method is not yet implemented",
     "backup_cant_mount_uncompress_archive": "Unable to mount in readonly mode the uncompress archive directory",
@@ -99,6 +106,7 @@
     "backup_method_copy_finished": "Backup copy finished",
     "backup_method_custom_finished": "Custom backup method '{method:s}' finished",
     "backup_method_tar_finished": "Backup tar archive created",
+    "backup_mount_archive_for_restore": "Preparing archive for restoration…",
     "backup_no_uncompress_archive_dir": "Uncompress archive directory doesn't exist",
     "backup_nothings_done": "There is nothing to save",
     "backup_output_directory_forbidden": "Forbidden output directory. Backups can't be created in /bin, /boot, /dev, /etc, /lib, /root, /run, /sbin, /sys, /usr, /var or /home/yunohost.backup/archives sub-folders",
@@ -106,7 +114,6 @@
     "backup_output_directory_required": "You must provide an output directory for the backup",
     "backup_output_symlink_dir_broken": "You have a broken symlink instead of your archives directory '{path:s}'. You may have a specific setup to backup your data on an other filesystem, in this case you probably forgot to remount or plug your hard dirve or usb key.",
     "backup_php5_to_php7_migration_may_fail": "Could not convert your archive to support php7, your php apps may fail to restore (reason: {error:s})",
-    "backup_running_app_script": "Running backup script of app '{app:s}'…",
     "backup_running_hooks": "Running backup hooks…",
     "backup_system_part_failed": "Unable to backup the '{part:s}' system part",
     "backup_unable_to_organize_files": "Unable to organize files in the archive with the quick method",
@@ -146,6 +153,7 @@
     "diagnosis_monitor_network_error": "Can't monitor network: {error}",
     "diagnosis_monitor_system_error": "Can't monitor system: {error}",
     "diagnosis_no_apps": "No installed application",
+    "dpkg_is_broken": "You cannot do this right now because dpkg/apt (the system package managers) seems to be in a broken state... You can try to solve this issue by connecting through SSH and running `sudo dpkg --configure -a`.",
     "dnsmasq_isnt_installed": "dnsmasq does not seem to be installed, please run 'apt-get remove bind9 && apt-get install dnsmasq'",
     "domain_cannot_remove_main": "Cannot remove main domain. Set a new main domain first",
     "domain_cert_gen_failed": "Unable to generate certificate",
@@ -210,7 +218,7 @@
     "good_practices_about_admin_password": "You are now about to define a new administration password. The password should be at least 8 characters - though it is good practice to use longer password (i.e. a passphrase) and/or to use various kind of characters (uppercase, lowercase, digits and special characters).",
     "good_practices_about_user_password": "You are now about to define a new user password. The password should be at least 8 characters - though it is good practice to use longer password (i.e. a passphrase) and/or to use various kind of characters (uppercase, lowercase, digits and special characters).",
     "hook_exec_failed": "Script execution failed: {path:s}",
-    "hook_exec_not_terminated": "Script execution hasn\u2019t terminated: {path:s}",
+    "hook_exec_not_terminated": "Script execution did not finish properly: {path:s}",
     "hook_json_return_error": "Failed to read return from hook {path:s}. Error: {msg:s}. Raw content: {raw_content}",
     "hook_list_by_invalid": "Invalid property to list hook by",
     "hook_name_unknown": "Unknown hook name '{name:s}'",
@@ -464,6 +472,7 @@
     "ssowat_persistent_conf_write_error": "Error while saving SSOwat persistent configuration: {error:s}. Edit /etc/ssowat/conf.json.persistent file to fix the JSON syntax",
     "system_upgraded": "The system has been upgraded",
     "system_username_exists": "Username already exists in the system users",
+    "this_action_broke_dpkg": "This action broke dpkg/apt (the system package managers)... You can try to solve this issue by connecting through SSH and running `sudo dpkg --configure -a`.",
     "unbackup_app": "App '{app:s}' will not be saved",
     "unexpected_error": "An unexpected error occured: {error}",
     "unit_unknown": "Unknown unit '{unit:s}'",
diff --git a/src/yunohost/app.py b/src/yunohost/app.py
index 19a308ffc..de759f04f 100644
--- a/src/yunohost/app.py
+++ b/src/yunohost/app.py
@@ -97,6 +97,9 @@ def app_fetchlist(url=None, name=None):
         name -- Name of the list
         url -- URL of remote JSON list
     """
+    if not url.endswith(".json"):
+        raise YunohostError("This is not a valid application list url. It should end with .json.")
+
     # If needed, create folder where actual appslists are stored
     if not os.path.exists(REPO_PATH):
         os.makedirs(REPO_PATH)
@@ -564,6 +567,9 @@ def app_upgrade(auth, app=[], url=None, file=None):
         url -- Git url to fetch for upgrade
 
     """
+    if packages.dpkg_is_broken():
+        raise YunohostError("dpkg_is_broken")
+
     from yunohost.hook import hook_add, hook_remove, hook_exec, hook_callback
 
     # Retrieve interface
@@ -574,28 +580,31 @@ def app_upgrade(auth, app=[], url=None, file=None):
     except YunohostError:
         raise YunohostError('app_no_upgrade')
 
-    upgraded_apps = []
+    not_upgraded_apps = []
 
     apps = app
-    user_specified_list = True
     # If no app is specified, upgrade all apps
     if not apps:
+        # FIXME : not sure what's supposed to happen if there is a url and a file but no apps...
         if not url and not file:
             apps = [app["id"] for app in app_list(installed=True)["apps"]]
-            user_specified_list = False
     elif not isinstance(app, list):
         apps = [app]
 
-    logger.info("Upgrading apps %s", ", ".join(app))
+    # Remove possible duplicates
+    apps = [app for i,app in enumerate(apps) if apps not in apps[:i]]
+
+    # Abort if any of those app is in fact not installed..
+    for app in [app for app in apps if not _is_installed(app)]:
+        raise YunohostError('app_not_installed', app=app)
+
+    if len(apps) == 0:
+        raise YunohostError('app_no_upgrade')
+    if len(apps) > 1:
+        logger.info(m18n.n("app_upgrade_several_apps", apps=", ".join(apps)))
 
     for app_instance_name in apps:
         logger.info(m18n.n('app_upgrade_app_name', app=app_instance_name))
-        installed = _is_installed(app_instance_name)
-        if not installed:
-            raise YunohostError('app_not_installed', app=app_instance_name)
-
-        if app_instance_name in upgraded_apps:
-            continue
 
         app_dict = app_info(app_instance_name, raw=True)
 
@@ -609,8 +618,7 @@ def app_upgrade(auth, app=[], url=None, file=None):
         elif app_dict["upgradable"] == "yes":
             manifest, extracted_app_folder = _fetch_app_from_git(app_instance_name)
         else:
-            if user_specified_list:
-                logger.success(m18n.n('app_already_up_to_date', app=app_instance_name))
+            logger.success(m18n.n('app_already_up_to_date', app=app_instance_name))
             continue
 
         # Check requirements
@@ -648,6 +656,7 @@ def app_upgrade(auth, app=[], url=None, file=None):
         if hook_exec(extracted_app_folder + '/scripts/upgrade',
                      args=args_list, env=env_dict)[0] != 0:
             msg = m18n.n('app_upgrade_failed', app=app_instance_name)
+            not_upgraded_apps.append(app_instance_name)
             logger.error(msg)
             operation_logger.error(msg)
         else:
@@ -675,14 +684,13 @@ def app_upgrade(auth, app=[], url=None, file=None):
                     os.system('cp -R %s/%s %s' % (extracted_app_folder, file_to_copy, app_setting_path))
 
             # So much win
-            upgraded_apps.append(app_instance_name)
             logger.success(m18n.n('app_upgraded', app=app_instance_name))
 
             hook_callback('post_app_upgrade', args=args_list, env=env_dict)
             operation_logger.success()
 
-    if not upgraded_apps:
-        raise YunohostError('app_no_upgrade')
+    if not_upgraded_apps:
+        raise YunohostError('app_not_upgraded', apps=', '.join(not_upgraded_apps))
 
     app_ssowatconf(auth)
 
@@ -705,6 +713,9 @@ def app_install(operation_logger, auth, app, label=None, args=None, no_remove_on
         no_remove_on_failure -- Debug option to avoid removing the app on a failed installation
         force -- Do not ask for confirmation when installing experimental / low-quality apps
     """
+    if packages.dpkg_is_broken():
+        raise YunohostError("dpkg_is_broken")
+
     from yunohost.hook import hook_add, hook_remove, hook_exec, hook_callback
     from yunohost.log import OperationLogger
 
@@ -798,6 +809,8 @@ def app_install(operation_logger, auth, app, label=None, args=None, no_remove_on
     operation_logger.related_to.append(("app", app_id))
     operation_logger.start()
 
+    logger.info(m18n.n("app_start_install", app=app_id))
+
     # Create app directory
     app_setting_path = os.path.join(APPS_SETTING_PATH, app_instance_name)
     if os.path.exists(app_setting_path):
@@ -874,6 +887,9 @@ def app_install(operation_logger, auth, app, label=None, args=None, no_remove_on
 
             app_ssowatconf(auth)
 
+            if packages.dpkg_is_broken():
+                logger.error(m18n.n("this_action_broke_dpkg"))
+
             if install_retcode == -1:
                 msg = m18n.n('operation_interrupted') + " " + error_msg
                 raise YunohostError(msg, raw_msg=True)
@@ -918,6 +934,8 @@ def app_remove(operation_logger, auth, app):
 
     operation_logger.start()
 
+    logger.info(m18n.n("app_start_remove", app=app))
+
     app_setting_path = APPS_SETTING_PATH + app
 
     # TODO: display fail messages from script
@@ -956,6 +974,9 @@ def app_remove(operation_logger, auth, app):
     hook_remove(app)
     app_ssowatconf(auth)
 
+    if packages.dpkg_is_broken():
+        raise YunohostError("this_action_broke_dpkg")
+
 
 def app_addaccess(auth, apps, users=[]):
     """
@@ -2181,6 +2202,11 @@ def _parse_action_args_in_yunohost_format(args, action_args, auth=None):
         if arg_type == 'boolean':
             arg_default = 1 if arg_default else 0
 
+        # do not print for webadmin
+        if arg_type == 'display_text' and msettings.get('interface') != 'api':
+            print(arg["text"])
+            continue
+
         # Attempt to retrieve argument value
         if arg_name in args:
             arg_value = args[arg_name]
@@ -2345,6 +2371,7 @@ def _parse_app_instance_name(app_instance_name):
     True
     """
     match = re_app_instance_name.match(app_instance_name)
+    assert match, "Could not parse app instance name : %s" % app_instance_name
     appid = match.groupdict().get('appid')
     app_instance_nb = int(match.groupdict().get('appinstancenb')) if match.groupdict().get('appinstancenb') is not None else 1
     return (appid, app_instance_nb)
diff --git a/src/yunohost/backup.py b/src/yunohost/backup.py
index 867de3ea9..53919f2cc 100644
--- a/src/yunohost/backup.py
+++ b/src/yunohost/backup.py
@@ -675,7 +675,7 @@ class BackupManager():
         tmp_app_bkp_dir = env_dict["YNH_APP_BACKUP_DIR"]
         settings_dir = os.path.join(self.work_dir, 'apps', app, 'settings')
 
-        logger.debug(m18n.n('backup_running_app_script', app=app))
+        logger.info(m18n.n("app_start_backup", app=app))
         try:
             # Prepare backup directory for the app
             filesystem.mkdir(tmp_app_bkp_dir, 0o750, True, uid='admin')
@@ -1254,6 +1254,8 @@ class RestoreManager():
         operation_logger = OperationLogger('backup_restore_app', related_to)
         operation_logger.start()
 
+        logger.info(m18n.n("app_start_restore", app=app_instance_name))
+
         # Check if the app is not already installed
         if _is_installed(app_instance_name):
             logger.error(m18n.n('restore_already_installed_app',
@@ -1814,10 +1816,11 @@ class TarBackupMethod(BackupMethod):
                 # Add the "source" into the archive and transform the path into
                 # "dest"
                 tar.add(path['source'], arcname=path['dest'])
-            tar.close()
         except IOError:
-            logger.error(m18n.n('backup_archive_writing_error'), exc_info=1)
+            logger.error(m18n.n('backup_archive_writing_error', source=path['source'], archive=self._archive_file, dest=path['dest']), exc_info=1)
             raise YunohostError('backup_creation_failed')
+        finally:
+            tar.close()
 
         # Move info file
         shutil.copy(os.path.join(self.work_dir, 'info.json'),
@@ -2078,6 +2081,7 @@ def backup_create(name=None, description=None, methods=[],
     backup_manager.collect_files()
 
     # Apply backup methods on prepared files
+    logger.info(m18n.n("backup_actually_backuping"))
     backup_manager.backup()
 
     logger.success(m18n.n('backup_created'))
@@ -2146,6 +2150,7 @@ def backup_restore(auth, name, system=[], apps=[], force=False):
     # Mount the archive then call the restore for each system part / app    #
     #
 
+    logger.info(m18n.n("backup_mount_archive_for_restore"))
     restore_manager.mount()
     restore_manager.restore()
 
diff --git a/src/yunohost/dyndns.py b/src/yunohost/dyndns.py
index 2f8d63135..2dadcef52 100644
--- a/src/yunohost/dyndns.py
+++ b/src/yunohost/dyndns.py
@@ -119,6 +119,9 @@ def dyndns_subscribe(operation_logger, subscribe_host="dyndns.yunohost.org", dom
         subscribe_host -- Dynette HTTP API to subscribe to
 
     """
+    if len(glob.glob('/etc/yunohost/dyndns/*.key')) != 0 or os.path.exists('/etc/cron.d/yunohost-dyndns'):
+        raise YunohostError('domain_dyndns_already_subscribed')
+
     if domain is None:
         domain = _get_maindomain()
         operation_logger.related_to.append(('domain', domain))
@@ -144,7 +147,8 @@ def dyndns_subscribe(operation_logger, subscribe_host="dyndns.yunohost.org", dom
                       'dnssec-keygen -a hmac-sha512 -b 512 -r /dev/urandom -n USER %s' % domain)
             os.system('chmod 600 /etc/yunohost/dyndns/*.key /etc/yunohost/dyndns/*.private')
 
-        key_file = glob.glob('/etc/yunohost/dyndns/*.key')[0]
+        private_file = glob.glob('/etc/yunohost/dyndns/*%s*.private' % domain)[0]
+        key_file = glob.glob('/etc/yunohost/dyndns/*%s*.key' % domain)[0]
         with open(key_file) as f:
             key = f.readline().strip().split(' ', 6)[-1]
 
@@ -152,9 +156,13 @@ def dyndns_subscribe(operation_logger, subscribe_host="dyndns.yunohost.org", dom
     # Send subscription
     try:
         r = requests.post('https://%s/key/%s?key_algo=hmac-sha512' % (subscribe_host, base64.b64encode(key)), data={'subdomain': domain}, timeout=30)
-    except requests.ConnectionError:
-        raise YunohostError('no_internet_connection')
+    except Exception as e:
+        os.system("rm -f %s" % private_file)
+        os.system("rm -f %s" % key_file)
+        raise YunohostError('dyndns_registration_failed', error=str(e))
     if r.status_code != 201:
+        os.system("rm -f %s" % private_file)
+        os.system("rm -f %s" % key_file)
         try:
             error = json.loads(r.text)['error']
         except:
@@ -333,7 +341,8 @@ def _guess_current_dyndns_domain(dyn_host):
     """
 
     # Retrieve the first registered domain
-    for path in glob.iglob('/etc/yunohost/dyndns/K*.private'):
+    paths = list(glob.iglob('/etc/yunohost/dyndns/K*.private'))
+    for path in paths:
         match = RE_DYNDNS_PRIVATE_KEY_MD5.match(path)
         if not match:
             match = RE_DYNDNS_PRIVATE_KEY_SHA512.match(path)
@@ -343,7 +352,9 @@ def _guess_current_dyndns_domain(dyn_host):
 
         # Verify if domain is registered (i.e., if it's available, skip
         # current domain beause that's not the one we want to update..)
-        if _dyndns_available(dyn_host, _domain):
+        # If there's only 1 such key found, then avoid doing the request
+        # for nothing (that's very probably the one we want to find ...)
+        if len(paths) > 1 and _dyndns_available(dyn_host, _domain):
             continue
         else:
             return (_domain, path)
diff --git a/src/yunohost/firewall.py b/src/yunohost/firewall.py
index 1c44efe99..9d209dbb8 100644
--- a/src/yunohost/firewall.py
+++ b/src/yunohost/firewall.py
@@ -195,6 +195,7 @@ def firewall_reload(skip_upnp=False):
 
     """
     from yunohost.hook import hook_callback
+    from yunohost.service import _run_service_command
 
     reloaded = False
     errors = False
@@ -276,8 +277,7 @@ def firewall_reload(skip_upnp=False):
         # Refresh port forwarding with UPnP
         firewall_upnp(no_refresh=False)
 
-    # TODO: Use service_restart
-    os.system("service fail2ban restart")
+    _run_service_command("reload", "fail2ban")
 
     if errors:
         logger.warning(m18n.n('firewall_rules_cmd_failed'))
diff --git a/src/yunohost/settings.py b/src/yunohost/settings.py
index bbfb3ca56..81ea46114 100644
--- a/src/yunohost/settings.py
+++ b/src/yunohost/settings.py
@@ -115,10 +115,18 @@ def settings_set(key, value):
         raise YunohostError('global_settings_unknown_type', setting=key,
                             unknown_type=key_type)
 
+    old_value = settings[key].get("value")
     settings[key]["value"] = value
-
     _save_settings(settings)
 
+    # TODO : whatdo if the old value is the same as
+    # the new value...
+    try:
+        trigger_post_change_hook(key, old_value, value)
+    except Exception as e:
+        logger.error("Post-change hook for setting %s failed : %s" % (key, e))
+        raise
+
 
 def settings_reset(key):
     """
@@ -235,3 +243,45 @@ def _save_settings(settings, location=SETTINGS_PATH):
             settings_fd.write(result)
     except Exception as e:
         raise YunohostError('global_settings_cant_write_settings', reason=e)
+
+
+# Meant to be a dict of setting_name -> function to call
+post_change_hooks = {}
+
+
+def post_change_hook(setting_name):
+    def decorator(func):
+        assert setting_name in DEFAULTS.keys(), "The setting %s does not exists" % setting_name
+        assert setting_name not in post_change_hooks, "You can only register one post change hook per setting (in particular for %s)" % setting_name
+        post_change_hooks[setting_name] = func
+        return func
+    return decorator
+
+
+def trigger_post_change_hook(setting_name, old_value, new_value):
+    if setting_name not in post_change_hooks:
+        logger.debug("Nothing to do after changing setting %s" % setting_name)
+        return
+
+    f = post_change_hooks[setting_name]
+    f(setting_name, old_value, new_value)
+
+
+# ===========================================
+#
+# Actions to trigger when changing a setting
+# You can define such an action with :
+#
+# @post_change_hook("your.setting.name")
+# def some_function_name(setting_name, old_value, new_value):
+#     # Do some stuff
+#
+# ===========================================
+
+
+#@post_change_hook("example.int")
+#def myfunc(setting_name, old_value, new_value):
+#    print("In hook")
+#    print(setting_name)
+#    print(old_value)
+#    print(new_value)
diff --git a/src/yunohost/tools.py b/src/yunohost/tools.py
index a220e21ca..a011b1546 100644
--- a/src/yunohost/tools.py
+++ b/src/yunohost/tools.py
@@ -524,6 +524,10 @@ def tools_upgrade(operation_logger, auth, ignore_apps=False, ignore_packages=Fal
         ignore_packages -- Ignore APT packages upgrade
 
     """
+    from yunohost.utils import packages
+    if packages.dpkg_is_broken():
+        raise YunohostError("dpkg_is_broken")
+
     failure = False
 
     # Retrieve interface
@@ -713,6 +717,22 @@ def tools_diagnosis(auth, private=False):
 def _check_if_vulnerable_to_meltdown():
     # meltdown CVE: https://security-tracker.debian.org/tracker/CVE-2017-5754
 
+    # We use a cache file to avoid re-running the script so many times,
+    # which can be expensive (up to around 5 seconds on ARM)
+    # and make the admin appear to be slow (c.f. the calls to diagnosis
+    # from the webadmin)
+    #
+    # The cache is in /tmp and shall disappear upon reboot
+    # *or* we compare it to dpkg.log modification time
+    # such that it's re-ran if there was package upgrades
+    # (e.g. from yunohost)
+    cache_file = "/tmp/yunohost-meltdown-diagnosis"
+    dpkg_log = "/var/log/dpkg.log"
+    if os.path.exists(cache_file):
+        if not os.path.exists(dpkg_log) or os.path.getmtime(cache_file) > os.path.getmtime(dpkg_log):
+            logger.debug("Using cached results for meltdown checker, from %s" % cache_file)
+            return read_json(cache_file)[0]["VULNERABLE"]
+
     # script taken from https://github.com/speed47/spectre-meltdown-checker
     # script commit id is store directly in the script
     file_dir = os.path.split(__file__)[0]
@@ -722,6 +742,7 @@ def _check_if_vulnerable_to_meltdown():
     # example output from the script:
     # [{"NAME":"MELTDOWN","CVE":"CVE-2017-5754","VULNERABLE":false,"INFOS":"PTI mitigates the vulnerability"}]
     try:
+        logger.debug("Running meltdown vulnerability checker")
         call = subprocess.Popen("bash %s --batch json --variant 3" %
                                 SCRIPT_PATH, shell=True,
                                 stdout=subprocess.PIPE,
@@ -735,6 +756,14 @@ def _check_if_vulnerable_to_meltdown():
         output, err = call.communicate()
         assert call.returncode in (0, 2, 3), "Return code: %s" % call.returncode
 
+        # If there are multiple lines, sounds like there was some messages
+        # in stdout that are not json >.> ... Try to get the actual json
+        # stuff which should be the last line
+        output = output.strip()
+        if "\n" in output:
+            logger.debug("Original meltdown checker output : %s" % output)
+            output = output.split("\n")[-1]
+
         CVEs = json.loads(output)
         assert len(CVEs) == 1
         assert CVEs[0]["NAME"] == "MELTDOWN"
@@ -744,6 +773,8 @@ def _check_if_vulnerable_to_meltdown():
         logger.warning("Something wrong happened when trying to diagnose Meltdown vunerability, exception: %s" % e)
         raise Exception("Command output for failed meltdown check: '%s'" % output)
 
+    logger.debug("Writing results from meltdown checker to cache file, %s" % cache_file)
+    write_to_json(cache_file, CVEs)
     return CVEs[0]["VULNERABLE"]
 
 
diff --git a/src/yunohost/utils/packages.py b/src/yunohost/utils/packages.py
index 5ef97618b..e10de6493 100644
--- a/src/yunohost/utils/packages.py
+++ b/src/yunohost/utils/packages.py
@@ -19,6 +19,7 @@
 
 """
 import re
+import os
 import logging
 from collections import OrderedDict
 
@@ -470,3 +471,13 @@ def ynh_packages_version(*args, **kwargs):
         'yunohost', 'yunohost-admin', 'moulinette', 'ssowat',
         with_repo=True
     )
+
+
+def dpkg_is_broken():
+    # If dpkg is broken, /var/lib/dpkg/updates
+    # will contains files like 0001, 0002, ...
+    # ref: https://sources.debian.org/src/apt/1.4.9/apt-pkg/deb/debsystem.cc/#L141-L174
+    if not os.path.isdir("/var/lib/dpkg/updates/"):
+        return False
+    return any(re.match("^[0-9]+$", f)
+               for f in os.listdir("/var/lib/dpkg/updates/"))